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HomeScience and NatureWebb Validates Hubble’s Distance Measurements

Webb Validates Hubble’s Distance Measurements

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New observations from the NASA/ESA/CSA James Webb Space Telescope confirms previous measurements by the NASA/ESA Hubble Space Telescope of distances between nearby stars and galaxies, offering a crucial cross-check to address the mismatch in measurements of the Universe’s mysterious expansion. Known as the Hubble tension, the discrepancy remains unexplained even by the best cosmology models.

This artist’s impression shows the evolution of the Universe beginning with the Big Bang on the left followed by the appearance of the Cosmic Microwave Background. The formation of the first stars ends the cosmic dark ages, followed by the formation of galaxies. Image credit: M. Weiss / Harvard-Smithsonian Center for Astrophysics.

“The discrepancy between the observed expansion rate of the Universe and the predictions of the Standard Model suggests that our understanding of the Universe may be incomplete,” said Nobel laureate and Johns Hopkins University’s Professor Adam Riess.

“With two NASA flagship telescopes now confirming each other’s findings, we must take this problem very seriously — it’s a challenge but also an incredible opportunity to learn more about our Universe.”

The new research builds on Professor Riess’ Nobel Prize-winning discovery that the Universe’s expansion is accelerating owing to a mysterious dark energy permeating vast stretches of space between stars and galaxies.

The authors used the largest sample of Webb data collected over its first two years in space to verify the Hubble telescope’s measure of the expansion rate of the Universe, a number known as the Hubble constant.

They used three different methods to measure distances to galaxies that hosted supernovae, focusing on distances previously gauged by the Hubble telescope and known to produce the most precise ‘local’ measurements of this number.

Observations from both telescopes aligned closely, revealing that Hubble’s measurements are accurate and ruling out an inaccuracy large enough to attribute the tension to an error by Hubble.

Still, the Hubble constant remains a puzzle because measurements based on telescope observations of the present Universe produce higher values compared to projections made using the Standard Model of cosmology, a widely accepted framework of how the Universe works calibrated with data of cosmic microwave background, the faint radiation left over from the Big Bang.

While the Standard Model yields a Hubble constant of about 67-68 km per second per megaparsec, measurements based on telescope observations regularly give a higher value of 70 to 76, with a mean of 73 km per second per megaparsec.

This mismatch has perplexed cosmologists for over a decade because a 5-6 km per second per megaparsec difference is too large to be explained simply by flaws in measurement or observational technique.

Since Webb’s new data rule out significant biases in Hubble’s measurements, the Hubble tension may stem from unknown factors or gaps in cosmologists’ understanding of physics yet to be discovered,.

“The Webb data are like looking at the Universe in high definition for the first time and really improves the signal-to-noise of the measurements,’’ said Siyang Li, a graduate student at Johns Hopkins University.

This image, taken with the Nicholas U. Mayall 4-m telescope, shows the spiral galaxy Messier 106. Two dwarf galaxies also appear in the image: NGC 4248 in the lower right and UGC 7356 in the lower left. Image credit: KPNO / NOIRLab / NSF / AURA / M.T. Patterson, New Mexico State University / T.A. Rector, University of Alaska Anchorage / M. Zamani & D. de Martin.

The astronomers covered roughly a third of Hubble’s full galaxy sample, using the known distance to the spiral galaxy Messier 106 (also known as M106 or NGC 4258) as a reference point.

Despite the smaller dataset, they achieved impressive precision, showing differences between measurements of under 2% — far smaller than the approximately 8-9% size of the Hubble tension discrepancy.

In addition to their analysis of pulsating stars called Cepheid variables, the gold standard for measuring cosmic distances, they cross-checked measurements based on carbon-rich stars and the brightest red giants across the same galaxies.

All galaxies observed by Webb together with their supernovae yielded a Hubble constant of 72.6 km per second per megaparsec, nearly identical to the value of 72.8 km per second per megaparsec found by Hubble for the very same galaxies.

“One possible explanation for the Hubble tension would be if there was something missing in our understanding of the early Universe, such as a new component of matter — early dark energy — that gave the Universe an unexpected kick after the Big Bang,” said Johns Hopkins University cosmologist Marc Kamionkowski, who was not involved in the study.

“And there are other ideas, like funny dark matter properties, exotic particles, changing electron mass, or primordial magnetic fields that may do the trick. Theorists have license to get pretty creative.”

The results were published in the Astrophysical Journal.

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Adam G. Riess et al. 2024. JWST Validates HST Distance Measurements: Selection of Supernova Subsample Explains Differences in JWST Estimates of Local H0. ApJ 977, 120; doi: 10.3847/1538-4357/ad8c21

Source : Breaking Science News

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